It has been well known that polysaccharides and derivatives thereof such as ester or carbamate derivatives of cellulose or amylose show a high optical resolving power. It has been also well known that chromatographic separating agents wherein these substances are physically adsorbed or held on silica gel are excellent separating agents having an optical resolving power over a wide range, a good theoretical plate number and a good durability (Y. Okamoto, M. Kawashima and K. Hatada, J. Am. Chem. Soc., 106, 5357, (1984)).
However, these separating agents can be employed only under restricted separation conditions, since polysaccharide derivatives are held on silica gel via physical adsorption and thus solvents in which the polysaccharide derivatives are soluble cannot be used as the mobile phase, etc. Also, solvents in which samples are to be dissolved are restricted. In the case of a sample having a low solubility in solvents usable as the mobile phase, there arises a serious problem particularly in chromatographic separation. Moreover, there is another inconvenience that only limited washing fluids are usable in washing away contaminants strongly adsorbed on the separating agents. Considering these points, there have been required separating agents carrying polysaccharide derivatives thereon and having a high solvent resistance.
To solve these problems, there have been developed a method wherein polysaccharide derivatives are chemically bonded directly to silica gel, a method wherein polysaccharide derivative molecules are crosslinked with each other and a method wherein a high solvent resistance is established by combining these two methods (JP-A 62-270602, JP-A 4-202141, JP-A 7-25904, JP-A 7-138301, JP-A 8-59702, WO95/18833, WO96/27615, WO97/4011 and WO97149733).
However, these techniques have the disadvantage of necessitating multi-step production processes, since unreacted hydroxyl or polyfunctional groups should be incorporated onto substituents for crosslinking or chemically bonding polysaccharide derivatives.
Accordingly, it has been required to develop separating agents for optical isomers which have the high optical resolving power inherent in polysaccharide derivatives together with a high solvent resistance and which can be produced through short process steps.